linux-kernel - Re: [PATCH v6] usb: gadget: udc: renesas_usb3: Fix use after free bug in renesas_usb3

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Message-ID: <CAJedcCzFhn90bSvd3S0=1rfrxAzVbjdxRsoRfqCCWuoa8m23OQ@mail.gmail.com>
Date:   Fri, 17 Mar 2023 02:11:09 +0800
From:   Zheng Hacker <hackerzheng666@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Zheng Wang <zyytlz.wz@....com>, p.zabel@...gutronix.de,
        biju.das.jz@...renesas.com, phil.edworthy@...esas.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        1395428693sheep@...il.com, alex000young@...il.com,
        yoshihiro.shimoda.uh@...esas.com
Subject: Re: [PATCH v6] usb: gadget: udc: renesas_usb3: Fix use after free bug
 in renesas_usb3_remove due to race condition

Greg KH <gregkh@...uxfoundation.org> 于2023年3月17日周五 02:09写道：
>
> On Fri, Mar 17, 2023 at 01:54:57AM +0800, Zheng Wang wrote:
> > In renesas_usb3_probe, role_work is bound with renesas_usb3_role_work.
> > renesas_usb3_start will be called to start the work.
> >
> > If we remove the driver which will call usbhs_remove, there may be
> > an unfinished work. The possible sequence is as follows:
> >
> > Fix it by canceling the work before cleanup in the renesas_usb3_remove.
> >
> > Note that removing a driver is a root-only operation, and should never
> > happen.
> >
> > CPU0                                          CPU1
> >
> >                                       | renesas_usb3_role_work
> > renesas_usb3_remove                   |
> > usb_role_switch_unregister|
> > device_unregister                     |
> > kfree(sw)                                             |
> > free usb3->role_sw                    |
> >                                       | usb_role_switch_set_role
> >                                       | //use usb3->role_sw
>
> Please use spaces for this, as something went wrong and it does not line
> up :(

Oh yes, will do in the next version. Thanks  for your advice :)

Best regards,
Zheng